Field of the Invention
This invention is directed to a stable, more useful form of lithium, lithium alloys and substrates coated with lithium, particularly suited for use as anodes in secondary electrochemical cells. This invention also relates to high energy density electrochemical cells. A lithium anode in such a cell is highly desirable because the use of a lithium anode results in useful voltage at a very low equivalent weight. The anode is the electrode which undergoes oxidation during the discharge portion of the discharge-charge cycle.
Lithium, however, tends to react with the organic electrolyte in the cell. When this happens, the reacted lithium is lost for recycling purposes thereby reducing the efficiency of the cell. Such loss can lead to premature destruction of the cell. The reaction products of the lithium and the organic electrolyte are deposited on the anode, eventually effectively insulating the anode from participation in the electrochemical reactions of the cell, thereby leading to cell failure.
Furthermore, lithium tends to form dendrites during recharge. These dendrites, which are nodular, poorly adhering forms of lithium, tend to fall from the anode and become isolated from the electrochemical reactions of the cell, a process known as "lithium isolation". Additionally, the dendrites may eventually lead to short circuiting of the cell if bridging by the lithium from the anode to the cathode takes place.
This invention is directed to enhancing a surface of lithium metal by creating a conducting layer of polymeric design. The enhanced lithium surface finds use in the fabrication of improved electrochemical cells and batteries made from lithium electrodes.